Abstract

Multivariate analyses were used to describe morphological variation in a population of red swamp crawfish, Procambarus clarkii, to ascertain the usefulness of this approach for ecological, quantitative genetic, and stock differentiation studies. Twelve body size traits were measured on 1,155 crawfish. Data were subjected to principal components analysis and subsequent factor analysis. Three non-orthogonal descriptive dimensions (factors) were identified. Factors were interpreted as variation in (1) relative size of chelae and carapace (which varied similarly), (2) relative size of the abdomen, and (3) variation in overall size resulting from environmental and genetic effects exclusive of density. These dimensions accounted for about 40%, 20%, and 19% of the total observed variation. Analyses of variance comparing factor scores of females, reproductively mature (Form I) males, and immature (Form II or juvenile) males indicated females have larger abdomens than males, mature males have larger forebodies than females, and immature males have smaller abdomens than mature males (P < 0.05 for all comparisons). Correlations between individual variables and factors (factor loadings) exhibited similar patterns for all three groupings. Factors appear to represent stable dimensions describing multivariate variation in P. clarkii.

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